The present invention generally relates to meltblowing apparatus for dispensing thermoplastic filaments and, more particularly, apparatus for meltblowing multi-component filaments.
Meltblowing technology is used in many different applications and industries including, for example, in adhesive dispensing and nonwoven material manufacturing. This technology generally involves extruding fine diameter filaments of thermoplastic material from a row of discharge outlets and impinging the extruded filaments with pressurized air immediately upon discharge. The pressurized air may be discharged as continuous sheets or curtains on opposite sides of the discharged filaments or as individual streams associated with the filament discharge outlets. The pressurized air is often referred to as process or primary air. This air draws down or attenuates the filament diameter while the filaments are airborne. The filaments are then randomly dispersed onto a substrate or a carrier.
For certain applications, it is desirable to utilize multiple types of thermoplastic liquid materials to form individual cross-sectional portions of each filament. Often, these multi-component filaments comprise two components and, therefore, are referred to as bicomponent filaments. For example, when manufacturing nonwoven materials for use in the garment industry, it may be desirable to produce bicomponent filaments having a sheath-core construction. The sheath may be formed from a softer material which is comfortable to the skin of an individual and the core may be formed from a stronger, but perhaps less comfortable material having greater tensile strength to provide durability to the garment. Another important consideration involves cost of the material. For example, a core of inexpensive material may be combined with a sheath of more expensive material. For example, the core may be formed from polypropylene or nylon and the sheath may be formed from a polyester or co-polyester. Many other multi-component fiber configurations exist, including side-by-side, tipped, and microdenier configurations, each having its own special applications. Various material properties can be controlled using one or more of the component liquids. These include, as examples, thermal, chemical, electrical, optical, fragrance, and anti-microbial properties. Likewise, many types of die tips exist for combining the multiple liquid components just prior to discharge to produce filaments of the desired cross-sectional configuration.
One problem associated with multi-component meltblowing apparatus involves the cost and complexity of the manifolds used to transmit each of the separate component liquids to the multi-component die tip. Typical manifolds must be machined with many different passages leading to the die tip to ensure that the proper flow of each component liquid reaches the die tip under the proper pressure and temperature conditions. These manifolds are therefore relatively complex and expensive components of the multi-component meltblowing apparatus.
For these reasons, it would be desirable to provide a meltblowing apparatus having a manifold system which may be easily manufactured and yet fulfils the requirement of effectively transmitting each of the component liquids to the multi-component die tip.
The present invention therefore provides an apparatus for meltblowing multiple types of liquid materials into multi-component filaments including a unique manifold structure coupled with a multicomponent die tip. In one general aspect, the apparatus comprises an intermediate manifold element having first and second opposite surfaces. First and second outer manifold elements respectively couple to the first and second opposite surfaces and have respective opposed surfaces. Each opposed surface respectively abuts one of the first and second opposite surfaces of the intermediate manifold elements. A first channel is formed between the opposed surface of the first outer manifold element and the first opposite surface of the intermediate manifold element. A second channel is formed between the opposed surface of the second outer manifold element and the second opposite surface of the intermediate manifold element. The first and second channels have inlets for respectively receiving the first and second liquids and outlets for respectively discharging the first and second liquids. These inlets and outlets may be formed in the intermediate manifold element, in the outer manifold elements, or between the intermediate manifold element and the respective outer manifold elements. The first and second channels may comprise recesses formed in the first and second opposite surfaces of the intermediate manifold element, or recesses formed in the opposed surfaces of the first and second outer manifold elements, or any combination thereof which forms the necessary channels.
A die tip is coupled adjacent the manifold elements and includes a plurality of multi-component filament discharge outlets. The die tip further includes at least first and second liquid distribution passages adapted to receive the first and second liquids respectively from the first and second channels. A liquid combining member communicates between the first and second liquid distribution passages and the filament discharge outlets. The liquid combining member receives the first and second liquids combines these liquids into respective multi-component filaments of a desired cross-sectional configuration just prior to discharge. Air discharge outlets are positioned adjacent the filament discharge outlets for supplying pressurized air to impinge the multi-component filaments upon discharge from the die tip.
In a more specific preferred embodiment of the manifold structure, the first and second outer manifold elements have respective recesses and, more preferably, a plurality of recesses on their respective opposed surface. The intermediate manifold element is coupled between the respective opposed surfaces of the first and second outer manifold elements. The recesses on the respective first and second opposite surfaces of the intermediate manifold element communicate, and preferably align with corresponding recesses on the opposed surfaces of the first and second outer manifold elements. The communicating recesses together form at least first and second channels and, preferably, first and second pluralities of channels each having a liquid inlet and a liquid outlet communicating with the die tip on the opposite sides of the intermediate manifold element.
Various advantages, objectives, and features of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings.